The biceps flexes the arm it does not extend it (straightens). The triceps brachii extends the arm. They do work together. If one is damaged and doesn't work as it should, the movement will be "jerky" and not smooth.
Two muscles are needed, one to extend the other to close
bicep- it bends the arm while the triceps straighten the arm.
biceps and triceps
Muscles in your arm.These are the muscles of your upper arm.
forearm and upper arm muscles.
deltoids; biceps,triceps
The arm is made up of two main muscles (biceps & triceps) for the arm to move one of these muscles must contract and the other must relax. Which muscle does which depends on which way you are moving your arm.Additional answerThis does not mention the muscles in the forearm, which mainly move the hand, or the muscle in the shoulder, deltoid, which lifts the arm.
Abduction of the arm is caused by contraction of the deltoid and supraspinatus muscles, which pull the arm away from the body. This movement allows for raising the arm to the side and is important for various shoulder and arm activities. Injuries or neurological conditions affecting these muscles or their nerve supply can lead to difficulty with arm abduction.
there is only two muscles in the upper arm, the triceps and the biceps
Well you have two muscles in your arm: the bicep and tricep. In order to make the arm move the two muscles must flex while the other extends and vice versa. So the bicep flexes and the tricep extends (the arm is bent). The bicep extends and the tricep flexes (the arm is straight)
It means that you naturally move your arm with out thinking that your going to move it. There are two types of muscles; voluntary muscles and involuntary muscles. Voluntary muscles are muscles that you think about to move sometimes and involuntary muscles are muscles that you don't think about moving. An example of an involuntary muscle would be your heart and an example of a voluntary muscle would be your arm even though you don't really have to think about it when you move it.
for example when you eat a bologna sandwich on rye, the fulcrum in your arm levers the joints in your body. This causes there to be a friction between the two muscles, causing your elbow to properly bend.